1. Field of the Invention
The present invention relates to a solid-state image pickup apparatus with fast photometry with pixels increased and a signal reading out method therefor. More particularly, the invention relates to a solid-state image pickup apparatus, which includes an array of photosensitive cells integrated in higher density and arranged obliquely adjacent to each other, that is, in the co-called honeycomb structure having the lines or rows of cells offset from each other by a length equal to the half of the pitch of the cells in line or row, to accomplish an increased resolution, and which is advantageously applicable to an electronic still camera, an image input apparatus and the like.
2. Description of the Background Art
With reference to a solid-state image pickup apparatus taking the so-called honeycomb arrangement, various proposals have been disclosed in, for example, Japanese patent publication No. 31231/1992, and Japanese patent laid-open Nos. 77450/1994 and 136391/1998.
In the apparatus disclosed in Japanese patent publication No.31231/1992, first electrodes meander along photosensitive cells which are arranged in the offset manner, so as to form a wavy shape pattern, and second electrodes are formed in another wavy pattern opposite in phase to the former. Other photosensitive cells are arranged in a region where the first and second electrodes separate so as to enable a signal to be read out from each cells via means for selectively coupling with the second electrodes, in response to an enable signal supplied to the first electrode, thus further increasing the resolution and the sensitivity of the solid-state image pickup apparatus from conventional. In the publication, the photosensitive cells are exemplified as formed octagonal.
In Japanese patent laid-open publication No. 77450/1994, the shape of photosensitive cells is formed as a square which is one of diamond shapes, and each side thereof forms an angle of 45 degrees in a vertical direction, so that its aperture ratio is made to be high, thus miniaturizing the solid-state image pickup apparatus. Particularly, by adopting a honeycomb arrangement, an increase in a vertical resolution is achieved. Moreover, a micro-lens is disposed on each photosensitive cell, thus increasing a light receiving efficiency.
In Japanese patent laid-open publication No. 136391/1998, meandering charge transfer devices of two lines are arranged between photoelectric conversion devices in a column direction, which are disposed so as to be adjacent to each other in the same row and relatively shifted by approximately the half of the interval between themselves in the adjacent rows, and the charge transfer devices are used for transferring the charge from the photoelectric conversion devices obliquely adjacent to each other. A spurious signal aliasing such as moiré is suppressed while achieving a high-density integration of the photoelectric conversion devices and an increase in a photoelectric conversion efficiency.
In this case, color filter segments are arranged in the form of Bayer arrangement rotated by 45°. In this color filter arrangement, color G is arranged in an isotropic relation to color R/B in both row and column directions. Also, a honeycomb stripe pattern is used, where the same number of color filter segments for colors R, G and B are uniformly arranged. In this case, the shape of the color filter segments are a regular hexagon and set in a relationship where the center distances between adjacent photosensitive cells are all equal.
In the foregoing Japanese patent publication No. 31231/1992 and Japanese patent laid-open publication No. 77450/1994, attention is paid only to the structure of the device in aiming at a high-density integration. Moreover, in Japanese patent laid-open publication No. 136391/1998, descriptions for the structure and the shape of the device and the positional relation of the color filters are made. Then, descriptions of whole-pixel reading out using these relations are made.
By the way, it is apprehended that a high-density integration takes times for a reading out of signal charge obtained by a photoelectric conversion. For example, in a mode of controlling a light measurement or a photometry in which an automatic focus adjustment (AF) and an automatic exposure (AE) control are performed, there are demands for shortening a time required for reading out the signal charge and for finishing a preparation for an image pickup without delay. For photosensitive cells, the high-density integration of the image pickup devices and shortening of the time of the signal reading out are antinomic demand, which are contradictory to each other.
Particularly, when the signal is read out from the photosensitive cells adopting a honeycomb arrangement in the mode of controlling a light measurement, a breakthrough by a different method from conventional methods is needed.
In particular, to perform Automatic Exposure (AE) control or Automatic White Balance (AWB) adjustment, information on all colors is necessary, and single-color reading out as in the case of Automatic Focus adjustment (AF) is useless. High-speed signal reading out timed with a drive signal is desired when the image capturing with the AE and AWB controls is performed.